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(January 2006) A New Power Plateau with lower cost and safer Lithium-ion Technology
compiled by Shirley Georgi

Adobe Photoshop ImageA123 Systems notes that its M1 cells offer the highest commercially available power density of any Lithium-ion chemistry.  High  power products are able to pulse at discharge rates as high as 100C and deliver over 3000Watts/kilogram, over an order of magnitude better than conventional Lithium-ion cells.  With their low impedance and thermally conductive design, A123 cells can be continuously discharged to  100% depth of discharge (DOD) at 35C rate, a marked improvement over all other rechargeable battery alternatives.  

Not only does the technology have a  market in power tools - perhaps replacing some of the Nickel-cadmium market, but it also has potential for hybrid vehicles.  Because the M1  is only one-fifth the weight of its  Nickel-metal hydride counterpart ,   A123 Systems’ technology could also be a possible candidate for hybrid vehicles where better gas mileage and/or higher battery performance for the same weight could be obtained. The company is currently working with the U.S. Department of Energy as part of a major undertaking to develop battery materials for future use in hybrid vehicles.   (The chart and all graphics in the article are courtesy of A123 Systems.)
A123 Systems is commercializing a new Lithium-ion battery which they are proud to say has five times as much power  and will last 10 times longer than other Lithium-ion batteries before recharge.  A123’s first customer who will intorduce this battery for commercial purposes  is Black  & Decker; its DeWALT line of 36-Volt power tools ,with the A123 System battery,  will be available in 2006.  Contractors and carpenters will now have this high-power available in tools such as reciprocating and circular saws, impact wrenches, rotary hammers, jigsaws, flashlights and combo kits.

CEO David Vieau said, “We expect that our technology will have the same impact on high -power products as the introduction of first-generation Lithium-ion technology had on the development and commercialization of consumer electronics in the 1990s.” (Photo is courtesy of A123 System Corporation.) +

The company says it is using nanoscale science to create the next generation of Lithium-ion batteries.  Specifically, A123 Systems is using a nanoscale electrode technology to achieve new heights in power, safety and estended  life of the battery.   Research  was initiated at the Massachusetts Institute of Technology (MIT) .It was here at MIT where   Dr. Yet-MIng Chiang, a materials scientist, developed an inexpensive lithium metal phosphate cathode for the battery which can be charged  to 90% capacity in five minutes. The battery contains  materials that are  lower in cost than cobalt, which is currently the most popular material used in the cathode of Lithium-ion batteries.  A 123 Systems’ M1  battery  also has a higher level of thermal stability  because of the doped nano-phosphate material ; cobalt has less thermal stability.  (BD note: In an article, “More Powerful  Batteries” by Kevin Bullis, Technology Review, 11/21/05, Dr. Chaing is said to decline to give details of  A123’s current battery, including whether or not it uses iron.”  However, Dr. Chaing in describing the cathode does say the cathode has “an inexpensive metal phosphate.”)

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Looking closer at the technology

A123 Systems  highlights three characteristics of  its new nanoscale Lithium-ion battery - power, safety and extended life.

Power  A123 systems states that its M1 battery has the highest power available in a mass produced Lithin-ion cell.  (See chart, “Highest power avaiable in a mass produed in a Li Ion Cell”  for details on continuous discharge at 100% DOD, long pulse and instant pulse.)

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The M1 cells have an ability to charge to high capacity in 5 minutes or less.  Typical Lithium-ion take approximately 90 minutes to charge to a similar level.  This factor makes the battery an excellent candidate for power tools.  Fast charge will also be a key enabled for practical electric drive vehicles.   (See chart, “Charge Profile.”)

The packaging of the cells offers 4 times higher thermal conductivity than conventional Lithium-ion cylindrical cells.    A123 Systems notes that coupled with the industry’s lowest impedance, the most efficient temperature management can be obtained of all Lithium-ion cells on the market.  

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Safety Because the batteries do not use oxide active materials, the cells are intrinsically safe and the risk of explosions and thermal runaway are eliminated.  These active materials do not release oxygen and are not combustible if exposed to high temperature and or mechanical abuse.  (See chart, “Accelerated Rate Calorimetry Comparison For M1vs. other Lithium-ion ion Chemistries.”)

Since conventional Lithium-ion cells  have had  a  tendency  to cause burning and /or explosions when overcharged, the M1 battery was designed with materials which eliminate this problem. This is accomplished by having all of the lithium fully extracted from the cathode when the battery is fully charged; thus, there is no lithium available to plate on the anode in an overcharged state.  Typical conventional Lithium-ion cells extract only half of their lithium content when they reach their upper cut-off Voltage; this situation  can lead to a safety problem.  

A123 Systems also has a patent pending laser-welded multi-plate tubular construction that is vibration and abuse tolerant.  This design has a hermetic seal with extremely  low internal resistance.   

Extended Life  Record cycle  life (as shown in the chart, “Excellent cycle life performance”) is credited to its chemical stability and a flat plateau at a lower oxidation potential than other Lithium-ion chemistries.  At  low rates, M1 cells can deliver several thousands of cycles at 100% DOD.

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The battery also has a wide temperature range (-300C to 700C) at high-power pulses. (See chart, “Excellent Low Temperature Performance.”)

A123 Systems has made great gains in decreasing  impedance growth, which has been  one of the top failure modes of  a high power battery  and a major cause of power fade over the life of the battery.  The company’s technology (patent pending)  has created its battery in which  the internal resistance (impedance) decreases with use.   This is of great benefit for applications where long calendar life is critical, i.e., hybrid and elecric vehicles and medical devices.

Viewing the company

A123 Systems was founded in  2001 by Yet-Ming Chaing  (currently a professor at MIT), Bart Riley (V.P. of R&D at A123 Systems) and Ric Fulop (V.P of Business Development and Marketing at A123 Systems).  It is a privately held corporation whose major share holders include: Motorola, Qualcomm, Sequoia Capital, North Bridge Yankee Tek, Massachusetts Institute of Technology and OnPoint Technologies.          

               BD